Dome shaped roofs for covering round constructions such as tanks, sewage filter beds, halls and the like are already known in sizes which can be greater than 100 m in diameter. Such supporting constructions or frames are made up of load-bearing elements which form a plurality of irregular triangles, sometimes as required also four-sided units, which are joined at junction points in such a way as to resist bending. These frames support the actual roof covering of sheets which are secured to the frame elements by special clamping strips. As requirements demand such roofs can be fitted with attachments such as positive and negative pressure membrane valves, ventilation flaps and the like, man-holes, props or walkways, platforms for workmen etc.
In the case of a previously known version of such dome shaped roofs I-beam sections are employed as the supporting elements which are joined at their junction points by rivetting or bolting their side flanges to a lower and an upper round plate. This kind of design resulted in a relatively heavy and therefore expensive construction.
The object of the present invention is, while retaining the prescribed strength of the frame, to achieve a reduction in weight and, via the corresponding saving in material, to arrive at a more favourably priced roofing. This object is achieved by means of the design described hereinbelow.